The invention relates to a method of manufacturing a field-effect transistor substantially consisting of organic materials.
The invention also relates to a field-effect transistor substantially consisting of organic materials.
The invention further relates to an integrated circuit (IC) comprising such a field-effect transistor (FET).
An integrated circuit comprising field-effect transistors substantially consisting of organic materials, in short organic field-effect transistors, is well suited for those electronic applications where using an integrated circuit manufactured using silicon technology would be prohibitively expensive. Examples include electronic bar codes.
As is well known by those skilled in the art, if an IC is to perform its task, it is imperative that the integrated logic gates, such as invertors, NOR and NAND gates, attain voltage amplification at the operating voltage. In order to attain voltage amplification, each individual field-effect transistor must be operated in a saturated regime, which is the regime where the channel transconductance exceeds the channel conductance.
A method of the type mentioned in the opening paragraph, which provides an organic FET satisfying said condition for voltage amplification is known from an article by Garnier et al. published in Science, vol. 265 (1994), pp. 1684-1686. In said known method a 1.5 μm thick polyester film is framed and is printed on both sides with a graphite-filled polymer ink, so as to form a 10 μm thick gate electrode on the one side and a source and drain electrode on the other side. Between the source and drain a 40 nm semiconducting sexithiophene layer is then deposited using flash evaporation.
A disadvantage of the known method is that the organic FETs provided by the method satisfy the condition for voltage amplification only at rather high (negative) source drain voltages. Typically, the difference is 30 V or higher. For many electronic applications, such as battery operated applications, such a voltage is too high. Also, the method is not very practical, not least because it involves framing and printing on a layer of only 1.5 μm. Such a thin film is very fragile and easily ruptures while being handled, leading to a defective device.